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Title:  Interference Management For Vector Gaussian Multiple Access Channels 
Authors:  Padakandla, Arun 
Advisors:  Sundaresan, Rajesh 
Keywords:  Multiple Access Channel (MAC) Multiplexing Data Communication Protocols Multiple Access Channels  Power Minimization Convex Optimization Multidimensional Signaling Colored Noise 
Submitted Date:  Mar2008 
Series/Report no.:  G22344 
Abstract:  In this thesis, we consider a vector Gaussian multiple access channel (MAC) with users demanding reliable communication at specific (Shannontheoretic) rates. The objective is to assign vectors and powers to these users such that their rate requirements are met and the sum of powers received is minimum.
We identify this power minimization problem as an instance of a separable convex optimization problem with linear ascending constraints. Under an ordering condition on the slopes of the functions at the origin, an algorithm that determines the optimum point in a finite number of steps is described. This provides a complete characterization of the minimum sum power for the vector Gaussian multiple access channel. Furthermore, we prove a strong duality between the above sum power minimization problem and the problem of sum rate maximization under power constraints.
We then propose finite step algorithms to explicitly identify an assignment of vectors and powers that solve the above power minimization and sum rate maximization problems. The distinguishing feature of the proposed algorithms is the size of the output vector sets. In particular, we prove an upper bound on the size of the vector sets that is independent of the number of users.
Finally, we restrict vectors to an orthonormal set. The goal is to identify an assignment of vectors (from an orthonormal set) to users such that the user rate requirements is met with minimum sum power. This is a combinatorial optimization problem. We study the complexity of the decision version of this problem. Our results indicate that when the dimensionality of the vector set is part of the input, the decision version is NPcomplete. 
URI:  http://hdl.handle.net/2005/702 
Appears in Collections:  Electrical Communication Engineering (ece)

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